Skid-resistant surfaces



United States Patent 3,479,202 SKID-RESISTANT SURFACES Daniel E. Groteke, Louisville, Ky., assignor to American Standard Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Dec. 17, 1965, Ser. No. 514,687

Int. Cl. B44d 1/52 US. Cl. 117-38 16 Claims ABSTRACT OF THE DISCLOSURE A method for imparting a skid-resistant surface to an enamelware article, which involves in combination the steps of providing a supply of particles of ceramic material, fusing the particles in an arc plasma, imparting a linear velocity to the fused particles, and impinging the fused particles on a surface of an enamelware article to be coated therewith.

This invention relates to enamelware. More specifically, this invention relates to methods for applying useful and decorative surface finishes to enameled article or portions thereof.

In many applications of enameled articles, the glossy surface normally characteristic of such articles is objectionable for one reason or another. In architectural applications, it may be desired to provide a matte finish for esthetic reasons or, particularly in exterior environments, to prevent objectionable glare from the glossy surface. In other cases, particularly in the production of bathtubs, shower floors and the like, the smoothness of the normal glossy surface is objectionable because of the hazard of slippage. Various methods have heretofore been proposed for developing matte or roughened surfaces on enameled articles, but in most cases they were less than wholly successful for a variety of reasons. In general, such methods resulted in the production of a surface characterized by minute surface irregularities. If, however, these irregularities were sufficiently large in size to afford any effective degree of non-skid action, they produced an undesirable sandy or unfinished appearance, and tended to trap and hold dirt, so that cleaning was diflicult.

Various methods have also been proposed for application of decorative colored designs to enameled surfaces. These have included a number of methods which involved the initial preparation of a liquid suspension of colored oxides, which could subsequently be applied either to fired or to unfired enamelware, and subsequently fired on. Other processes involved the application of the colorants in dry powder form to a fired or unfired piece, with an undercoating of fixative or the like, if needed, to hold the powdered colors in place until firing. All of these methods, although successful to some degree, suffer from certain disadvantages. Those in which the colorant is applied to the unfired enamelware article require that the design be applied in a form which will not run into the background color either prior to or during the firing.

In the case of colorants dispersed in liquid vehicles, this entails the necessity of carefully selecting the vehicle, and carefully controlling the application of the colorant to the enamelware piece and the subsequent firing. In the firing, particularly, careful control is needed to ensure that the coating is heated enough so as to reduce its viscosity to the point where it will form a properly cured, glossy finish, and yet not so much as to allow the background enamel and the colorant composition to run together, blurring the outlines of the design. The same necessity for careful control of the firing cycle prevails when the colorant is applied to the unfired enamelware article in the form of a dry powder.

When the design is applied to a fired article, it is possible to overcome this difiiculty to some extent by choosing a colorant enamel formulation that matures at a slightly lower firing temperature than the background enamel. The design can then be fired on at a somewhat lower temperature than used for the initial firing, so that the background coat is not reduced in viscosity sutficiently to run together with the colorant enamel and blur the outlines of the design. Methods which depend on a separate, additional firing to fuse the design onto the ware, however, suffer from the serious disadvantage, in that reheating the entire piece is costly in terms of fuel and of furnace capacity, and also provides additional opportunity for the development of thermally-induced stresses, which may lead to spalling, crazing and the like.

Most of the foregoing difficulties also apply to the methods heretofore proposed for the production of enamelware articles having skid-resistant or matte-finish surfaces.

Prior methods for developing skid-resistant surfaces on bathtubs have consisted of two primary methods? (a) removal of a portion of the enamel gloss by shot blasting or grit blasting, or (b) by an additional firing operation where some special powder or material is added on the hot piece of ware.

These methods are limited in acceptance because one method (grit blasting) removes the surface glaze of the enamel and exposes the covering to staining and corro sion, and the second (refiring) is limited in design possibilities because of the inconvenience of manipulation at the high temperatures required in enameling.

An object of this invention, therefore, is to provide improved methods for the production of enamelware articles having skid-resistant surfaces.

Another object is to provide methods for such articles, which do not present an undesirable sandy or unfinished appearance.

Still another object is to provide readily cleanable skidresistant enamelware articles.

Another object is to provide methods for production of skid-resistant surfaces on enamelware articles, which do not depend on removal of a portion of the enamel.

Another object is to provide improved methods for the application of colored designs and indicia to enamelware surfaces.

A further object is to provide methods whereby colored designs may be produced, while avoiding any tendency for the design to run into the enamel of the background color.

Yet another object is to provide methods for applying colored designs to fired enamelware articles, which do not require refiring of the articles in order to fuse the design material to the articles.

Another object is to provide methods whereby a design may be applied to an enamelware article while said article is either at ambient temperature or at elevated temperature, according to the convenience of the manufacturer.

A feature of the invention is the use of a plasma arc to fuse particles of ceramic colorant or translucent materials.

Another feature is the use of a spray technique to direct a stream of ceramic colorant or translucent particles against a surface to be coated therewith.

A further feature is the use of a plasma of inert gas particles as a suspending and transport medium for the fused particles of ceramic colorant.

Still another feature is the use of a plasma-arc torch to fuse, suspend and eject a stream of particles of ceramic colorant.

Other objects, features and advantages will become apparent from the following more complete description and claims.

In a particularly desirable embodiment, this invention contemplates a method for imparting a skid-resistant surface to an enamelware article, which comprises in combination the steps of providing a supply of particles of ceramic colorant material, fusing said particles in an arc plasma, imparting a linear velocity to said fused particles, impinging said fused particles on a surface of an article to be decorated therewith, and coating said surface with a vitreous deposit.

In practicing the process of this invention, it is convenient to use a conventional plasma arc spray system, equipped with a central electrode, an annular electrode surrounding the central electrode and spaced therefrom by an annular space, means for feeding a gas into the are produced in the annular space upon energization of the electrodes, and means for feeding a powdered material into the plasma produced by the action of the arc upon the gas. Such equipment is readily available on the market, for example the PG-100 spray system manufactured by Avco Manufacturing Co.

The choice of gas is not inherently critical, inasmuch as virtually any gaseous material may be converted to the plasma state by the action of the arc. Oxidizing or reducing gases may be used for certain purposes, for example to influence the state of oxidation and consequently the color of certain transition metal oxide colorants. In general, however, it is preferred to use a gas such as argon, nitrogen, helium, or hydrogen, or combinations of the same. A particularly desirable combination is a mixture of nitrogen and hydrogen, preferably in proportions of about 8 parts by volume of nitrogen to 1 part of hydrogen, for example at flow rates of 1.36 s.c.f.m. (standard cubic feet/minute) nitrogen and 0.17 s.c.f.m. hydrogen.

Virtually any solid, particulate material may be employed in the process of the invention, provided it can be heated appreciably beyond its melting point in the arc plasma without decomposing. For practical purposes it is preferred to use the materials commonly used in the ceramic arts, and particularly in the manufacture of enamelware, for example alumina, silica, feldspar, borax, soda ash and simple metallic oxides, or mixtures thereof.

For producing colored designs according to the method of the invention, any of the ceramic colorants commonly used for making colored vitreous enamels may be used, either alone or in simple admixture with other enamel ingredients such as those listed above, or preliminarily fused and ground to form a powdered enamel or frit composition. Typical of such pigments are various oxides of iron, oxides of other transition metals such as cobalt, nickel, manganese, etc. Cobalt oxide powder may be used in admixture with aluminum oxide, for example, to produce a pleasing blue deposit. Visual patterns may also be developed by the use of a white or translucent material on a colored background enamel. Pure alumina, for example, provides a translucent deposit which allows the background color to show through as a lighter tint, producing a pleasing effect. The expression ceramic colorant as used herein should therefore be understood to embrace materials of colors other than the color of the enamel coat, including white materials and translucent materials as used to modify the appearance of a colored background enamel.

A linear velocity is imparted to the fused particles by virtue of the fact that they are fed into, and become suspended in, the moving plasma jet. The motion of the plasma, in turn, results from the fact that the supporting gas is continuously fed into the rear of the annular arc space, and continuously emerges from the front as a plasma jet.

The article to be treated is placed in the path of the plasma jet with its burden of fused particles of ceramic material, close enough thereto so that the particles are still in the fused condition whe th im i on h face of the article. Upon striking the relatively cool surface of the enamelware article, the particles solidify after effecting a slight and transient surface fusion of the enamel coat, and remain firmly bound to the enamel.

Appropriate masking may be used to cause the particles to deposit in the form of decorative patterns, colored designs, lettering, etc., and the design of the mask is reproduced faithfully, the more so when the fused particles are produced from very finely ground powders.

The particle size of the powder feed is subject to considerable variation within the ambit of the invention. A useful range for most general purposes consists of particles ground to pass a 270-mesh sieve, but be retained on a 325-mesh sieve. Such a particle size range will produce a deposit having a surface roughness of approximately 250 r.m.s. microinches. Larger particles may be used where it is desired to produce a rougher deposit for improved skid-resistant properties, and smaller particles may be used where it is desired to produce extremely fine designs or indicia.

The distance between the nozzle of the plasma jet spray and the article to be treated may vary somewhat, for example, from about 2 to about 12 inches. A distance of about six inches has been found to be generally satisfactory, but depends to some extent upon the type of gas used to generate the plasma arc.

During the deposition, the spray is passed preferably translationally across the surface of the article being treated, rather than being .held stationary with respect thereto. Where heavy deposits of skid-resistant material are desired, it is preferred to make several rapid passes with the jet spray, rather than a single slow pass, as the buildup of several light deposits tends to provide a more uniform coating than is obtained by laying down a single heavy deposit.

What is claimed is:

1. A method for imparting a skid-resistant surface to an enamelware article, which comprises the following steps:

(i) providing a supply of particles of ceramic material, having a size ranging between about 270 to about 325 mesh;

(ii) fusing said particles in a plasma-arc torch having an exit nozzle;

(iii) holding the exit of said nozzle away from said enamelware article a distance not less than about 2 inches nor more than about 12 inches;

(iv) imparting a linear velocity to said fused particles;

and

(v) impinging said fused particles through said exit nozzle on a relatively cool surface of said enamelware article to effect a transient surface fusion of the enamelware article, whereby the particles solidify and remain firmly bound to the enamelware article to form a skid-resistant surface.

2. A method according to claim 1 wherein the particles of ceramic material include sizes smaller than 325-mesh and larger than 270-mesh.

3. The method of claim 1 wherein the roughness of the skid-resistant surface is about 250 R.M.S. micro-inches.

- 4. A method according to claim 1, wherein said fused particles are impinged upon said surface by suspending said particles in a plasma jet and placing said surface in the path of said jet.

5. A method according to claim 4, wherein said plasma jet is moved translationally over said surface during the impingment of said particles on said surface.

6. A method according to claim 1, wherein said arc plasma is generated by continuously passing a gas through an electrical arc.

7. A method according to claim 6, wherein said gas is selected from the group consisting of argon, helium, hydrogen, nitrogen and mixtures thereof.

8. A method according to claim 7, wherein said gas is a mixture of nitrogen and hydrogen.

9. A method for producing a colored design on a surface of an enamelware article which comprises the following steps: p

(i) providing a supply of particles of ceramic colorant material having a size ranging from about 270 to about 325 mesh;

(ii) fusing said particles in a plasma-arc torch having an exit nozzle;

(iii) holding the exit of said nozzle away from said enamelware article a distance not less than about 2 inches nor more than about 12 inches;

(iv) imparting a linear velocity to said fused particles;

and

(v) impinging said fused particles on a relatively cool surface of said enamelware article through said exit nozzle and through an interposed mask having a design therein to form a corresponding design on the enamelware article by effecting transient surface fusion of the enamelware article, the particles solidifying and remaining firmly bound to the enamelware article to form the colored design.

10. A method according to claim 9, wherein said ceramic colorant material is a material producing a translucent deposit on the enamelware article.

11. The method of claim 9 wherein the ceramic colorant material for the design is of a color different from the enamelware article.

12. A method according to claim 9, wherein said fused particles are impinged upon said surface by suspending said particles in a plasma jet and placing said surface in the path of said jet.

13. A method according to claim 12, wherein said plasma jet is moved translationally over said surface during the impingement of said particles on said surface.

14. A method according to claim 9, wherein said are plasma is generated by continuously passing a gas through an electrical arc.

15. A method according to claim 14, wherein said gas selected from the group consisting of argon, helium, hydrogen, nitrogen and mixtures thereof.

16. A method according to claim 15, wherein said gas is a mixture of nitrogen and hydrogen.

References Cited UNITED STATES PATENTS 2,292,369 8/1942 Gordon 117-40 2,960,594 11/1960 Thorpe.

3,003,220 10/1961 Bassett et a1. 117-40 3,035,937 5/1962 Baldauf et al 117-40 3,086,880 4/1963 Compton 117-40 3,197,335 7/1965 Leszynski 117105.2 XR 3,335,025 8/1967 Rightmire et al. 117-l05.2 XR

DAVID KLEIN, Primary Examiner US. Cl. X.R. 1l740, 46, 105.2 

